1. Field of the Invention
The present invention relates to a light source unit and a projector which includes the light source unit.
2. Description of the Related Art
In these days, data projectors are used on many occasions as image projection apparatuses which project images of screens and video images of personal computers, as well as images of image data stored in memory cards on to a screen. These projectors are such that light emitted from a light source is caused to converge to a micromirror device called DMD (Digital Micromirror Device) or a liquid crystal plate for display of a color image on the screen.
In projectors of the type described above, conventionally, projectors in which a high-intensity discharge lamp is used as a light source have been the mainstream of projectors. In recent years, however, there have been made many developments and proposals on light source units which use as a light source a light emitting diode or a laser diode, or devices using organic EL technology or luminescence technology using luminescent materials. For example, Japanese Unexamined Patent Publication No. 2004-341105 (JP-A-2004-341105) proposes a light source unit which includes a luminous wheel which is made up of a disc-shaped transparent base material and on which a luminescent material layer is disposed which receives ultraviolet light as excitation light emitted from a solid-state light source and converts the ultraviolet light so received into visible light and the solid-state light source. In the light source unit proposed in JP-A-2004-341105, ultraviolet light is shone on to the luminescent material layer formed on the surface of the luminous wheel as excitation light, so that different types of luminescent light of red, green and blue wavelength bands can be emitted. However, since the luminous efficiency of the red luminescent material is lower than those of the other luminescent materials, there has been caused a problem that the luminance of red becomes insufficient.